The present invention relates to a novel organosilicon compound not known in the prior art nor described in any publications. The compound has been unexpectedly discovered in the course of the investigations to obtain an efficient additive compound for improving shaped articles of various kinds of synthetic resins relative to flexibility, weatherability, cold resistance, curability and mechanical strengths. Related disclosures are found in U.S. Pat. No. 4,268,682 and in Kogakubu Kenkyu Hokoku, Chiba University, Japan, vol. 37, No. 2, pages 35-40 (1986) (Kojima et al.).